Many structures, including homes, have networks based on coaxial cable (“coax”).
The Multimedia over Coax Alliance (“MoCAT™”), provides at its website (www.mocalliance.org) an example of a specification (viz., that available under the trademark MoCA), which is hereby incorporated herein by reference in its entirety, for networking of digital information, including video information, through coaxial cable. The specification has been distributed to an open membership.
Technologies available under the trademark MoCA, and other specifications and related technologies (collectively, with MoCA, “the existing technologies”), often utilize unused bandwidth available on the coax. For example, coax has been installed in more than 70% of homes in the United States. Some homes have existing coax in one or more primary entertainment consumption locations such as family rooms, media rooms and master bedrooms. The existing technologies allow homeowners to utilize installed coax as a networking system for the acquisition and use of information with high quality of service (“QoS”).
The existing technologies may provide high speed (270 mbps), high QoS, and the innate security of a shielded, wired connection combined with packet-level encryption. Coax is designed for carrying high bandwidth video. Today, it is regularly used to securely deliver millions of dollars of pay-per-view and video content on a daily basis.
Existing technologies provide throughput through the existing coaxial cables to the places where the video devices are located in a structure without affecting other service signals that may be present on the cable.
The existing technologies work with access technologies such as asymmetric digital subscriber lines (“ADSL”), very high speed digital subscriber lines (“VDSL”), and Fiber to the Home (“FTTH”), which provide signals that typically enter the structure on a twisted pair or on an optical fiber, operating in a frequency band from a few hundred kilohertz to 8.5 MHz for ADSL and 12 MHz for VDSL. As services reach such a structure via any type of digital subscriber line (“xDSL”) or FTTH, they may be routed via the existing technologies and the coax to the video devices. Cable functionalities, such as video, voice and Internet access, may be provided to the structure, via coax, by cable operators, and use coax running within the structure to reach individual cable service consuming devices in the structure. Typically, functionalities of the existing technologies run along with cable functionalities, but on different frequencies.
The coax infrastructure inside the structure typically includes coax, splitters and outlets. Splitters typically have one input and two or more outputs and are designed to transmit signals in the forward direction (input to output), in the backward direction (output to input), and to isolate outputs from different splitters, thus preventing signals from flowing from one coax outlet to another. Isolation is useful in order to a) reduce interference from other devices and b) maximize power transfer from Point Of Entry (“POE”) to outlets for best TV reception.
Elements of the existing technologies are specifically designed to propagate backward through splitters (“insertion”) and from output to output (“isolation”). One outlet in a structure can be reached from another by a single “isolation jump” and a number of “insertion jumps.” Typically isolation jumps have an attenuation of 5 to 40 dB and each insertion jump attenuates approximately 3 dB. MoCA™-identified technology has a dynamic range in excess of 55 dB while supporting 200 Mbps throughput. Therefore MoCA™-identified technology can work effectively through a significant number of splitters.
Networks based on the existing technologies are often coordinated networks, in which a processing unit serves as a network coordinator. The coordinator defines medium access plan (“MAP”) cycles, prospectively assigns data transmission events to the cycles, and serially processes the cycles by executing or coordinating the events in each cycle. Coordinated network schemes, such as MoCA™-identified technology, may be used for transmission of streaming video and thus data throughput between outlets is desirable.
FIG. 1 shows known data flow 100 that may be implemented in a coordinated network. In data flow 100, network coordinator 102 grants only explicit reservation requests (i.e., a transmission opportunity is scheduled only to a granted reservation request made by the transmitter on a per frame or aggregated frame basis). Upon receiving reservation requests, network coordinator 102 grants and schedules transmission opportunities in the next MAP cycle. For example, network coordinator 102 grants transmission opportunities to requesting transmitter nodes such as transmitting node 104. Network coordinator 102 periodically allocates a reservation request opportunity (“RR Opportunity”), such as 106 in MAP Cycle i, to transmitting node 104. In response to RR Opportunity 106, transmitting node 104 transmits in MAP Cycle i+1 reservation request (“RR”) 108 for the transmission of data frame k. Network coordinator 102 responds in MAP Cycle i+1 by transmitting to transmitting node 104 frame k transmission grant 110. In MAP Cycle i+2, transmitting node 104 transmits data frame k to receiving node 112 in frame k transmission 111. Data flow 100 includes subsequent exchanges between network coordinator 102 and transmitting node 104 in connection with data frame m: viz., RR Opportunity 114, RR 116, frame m transmission grant 118 and frame m transmission 119.
Data flow 100 has an average latency of three MAP cycles between the receipt of an Ethernet packet by transmitting node 104 and reception of the packet at receiving node 112. In existing technologies such as that identified by MoCA™ the nominal MAP cycle duration is 1 millisecond (“ms”), yielding a temporal latency of 3 ms. Such latency may limit the ability of the existing technologies to support time sensitive applications such as Ethernet AV (audiovisual) Bridging, including class 5 AVB data transfer.
FIG. 2 shows typical communication network 200, which includes network segments 202, 204 and 206. Network segments 202 and 206 are Ethernet packet-switched segments and network segment 204 is a shared media packet mode network segment that requires a network coordinator. Packet-switched network segments 202 and 206 require architectural and message passing characteristics that are different from those required by packet mode network segment 204. For example, legacy switch 208 in packet switched segment 202 may not be configured for exchanging audiovisual data. As another example, Ethernet hub 210 in packet switched segment 204 may operate based on a half duplex protocol, whereas AV switch 212 in packet mode segment 206 may require a full duplex protocol. As a result of protocol mismatching, the quality of communication of audiovisual data from AV device 214 in segment 202 to device 216, which may be a display, in segment 204 may be degraded or be subject to latency delays.
It therefore would be desirable to provide systems and methods for reducing latency in coordinated networks.
It therefore also would be desirable to provide systems and methods for Ethernet AV bridging using shared media networks.